The present invention relates to a machining condition setting system in a wire cut electric discharge machine having a numerical control unit.
In conventional wire cut electric discharge machines, a predetermined voltage is applied to a gap formed between a workpiece and a wire electrode extending along the longitudinal direction of the machine in order to cut the workpiece by a small amount each time. At the same time, the wire electrode is moved relative to the workpiece in accordance with instruction data so as to produce a workpiece with a predetermined shape. An electric discharge machine of this type requires specific machining conditions such as a voltage applied to the gap, a peak value and an average value of a current which flows through the gap, a capacitance of a discharge circuit, a duty cycle of a pulse applied to the gap, a tension force acting on the wire electrode, and a resistivity of a working fluid supplied to the gap, depending on the material and thickness of the workpiece and a diameter of the wire electrode. An operator who operates the wire cut electric discharge machine must preset these machining conditions at an operation panel on the numerical control unit by considering the material and thickness of the workpiece and the diameter of the wire electrode.
However, in the conventional wire cut electric discharge machine, the machining conditions are preset by a rotary switch. For this reason, rotary switches must be provided for the respective machining conditions. When the preset values of the machining conditions are updated, it is difficult to gradually update these preset values. In addition to this disadvantage, when the preset values of the machining conditions change greatly during machining, hunting occurs and the wire electrode is undesirably cut. As a result, scratches are formed on the workpiece.